END OF A MISSION by Heinrich Boll. 207 pages. McGraw-Hill. $5.95.
Postwar German fiction has its mea culpa school, its black-humor crowd and its how-did-it-happen-to-us hand wringers. Heinrich Boll (Billiards at Half-Past Nine) constitutes a school of his own. His writing skills seem at first oldfashioned, but they always turn out to be just right for hitting his targets: hypocrisy, his countrymen's haste to forget the Hitlerite period, the greed of the fat-cat crowd. In this short caper, set in today's Rhineland, a German army Jeep is burned by an intelligent young soldier...